This application is based upon Japanese Patent Application No. HEI 11-184,468, filed Jun. 29, 1999, which is hereby expressly incorporated by reference in its entirety.
1. Field of the Invention
The present invention generally relates to closed loop cooling systems for land vehicles. More specifically, the present invention relates to such cooling systems featuring bypass arrangements to better moderate coolant temperature in low temperature operating environments.
2. Description of Related Art
Snowmobiles are popular land vehicles that are used primarily in the winter and in cold and snowy conditions. Snowmobiles are powered by internal combustion engines. To improve emissions, four cycle engines have been replacing two cycle engines in many snowmobiles. Such engines often feature a water cooling system. Such a cooling system circulates coolant or water through various cooling jackets designed to cool specific components of the engine. Often the coolant is circulated using a water pump that is constantly driven by the crankshaft or another shaft that is ultimately powered by the crankshaft.
Because the water pump is constantly driven, coolant begins circulating once the engine is turned over and remains circulating until the crankshaft stops turning. This is particularly disadvantageous in cold weather environments. For instance, lubricant viscosity changes as a function of lubricant temperature. Until an engine has properly warmed-up, the lubricant may not flow properly to various components. Additionally, decreased temperatures can affect pressures and combustion. Accordingly, circulating coolant prior to a preset warm-up temperature can be disadvantageous.
Accordingly, a cooling system is desired in which coolant can circulate once the engine has started but the coolant circuit can bypass a heat exchanger. Such an arrangement allows the engine to warm-up more rapidly and allows the coolant to bypass the heat exchanger until a present coolant temperature has been reached. Such an arrangement also can be used to help moderate coolant temperature in lower temperature environments.
One aspect of the present invention involves a land vehicle comprising an engine with a cooling jacket disposed within a portion of the engine and communicating with a heat exchanger. The heat exchanger is positioned in a location exposed to ambient air. The engine comprises a crankshaft and a peripheral engine component. The peripheral engine component comprises a cooling jacket. A water pump is drivingly connected to the crankshaft. A closed loop cooling system comprises a first water delivery conduit providing coolant to a switching valve arrangement, a second water delivery conduit providing coolant to the cooling jacket of the peripheral engine component and a water return line returning coolant to the water pump. The switching valve arrangement comprises a valve, a supply line extending to the heat exchanger and a bypass line. The valve is adapted to direct coolant through the heat exchanger if a sensed coolant temperature is above a preset temperature and to direct coolant through the bypass line if the sensed coolant temperature is below the preset temperature.
Another aspect of the present invention involves a snowmobile comprising a frame with at least one steerable ski supporting the frame. An engine is mounted to the frame and a heat exchanger is mounted to the frame. The engine comprises a crankshaft that is rotatably driven and a water pump that is driven by the crankshaft. The engine power a drive belt. A first cooling jacket is disposed within a portion of the engine. A peripheral component is mounted to the engine with a second cooling jacket extending through a portion of the peripheral component. A closed loop cooling system comprises the heat exchanger, the first cooling jacket, the second cooling jacket, the water pump and a switching valve arrangement. The switching valve arrangement is interposed between the water pump and the heat exchanger. The switching valve arrangement comprises a chamber, a supply line extending to the heat exchanger, a return line extending from the heat exchanger to the chamber and a bypass line extending into the chamber without extending through the heat exchanger. A valving assembly is disposed within the chamber and has a first position to direct a substantial flow through the heat exchange and a second position to direct a substantial flow around the heat exchanger. An actuator is adapted to move the valving assembly to the first position if a sensed coolant temperature is above a preset temperature and is adapted to move the valving assembly to the second position if a sensed coolant temperature is below a preset temperature.
A further aspect of the present invention involves a land vehicle comprising an engine with a first cooling jacket disposed within a portion of the engine and communicating with a heat exchanger. The heat exchanger is positioned in a location exposed to ambient air. The engine comprises a crankshaft and a peripheral engine component. The peripheral engine component comprises a second cooling jacket. A water pump is drivingly connected to the crankshaft. A closed loop cooling system communicates with the water pump, the first cooling jacket, the second cooling jacket and the heat exchanger. The cooling system comprises means for bypassing the heat exchanger if a sensed coolant temperature is below a preset temperature.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiment which follows.